Syringes are commonly used for hypodermic injection. In general, a conventional syringe includes a barrel which has a cavity for storing a desired fluid, a needle assembly which includes a needle and which is secured to the barrel, and a plunger rod which is selectively inserted or removed from the cavity.
Conventional syringes have various shortcomings and disadvantages. For example, a needle prick injury is a common problem suffered by users (e.g., medical practitioners) of conventional syringes. In order to prevent needle prick injuries, safety syringes have been developed. These safety syringes typically include a shield which secures the needle therein. A locking mechanism may also be included which allows the needle to be temporarily secured in the shield prior to use of the safety syringe and to be permanently locked therein after use of the safety syringe, thereby preventing further use of the safety syringe and preventing needle pricks.
Some of these safety syringes, however, require complicated designs which result in increased manufacturing, distribution, and stocking costs. Because of such costs, it may not be feasible to replace conventional non-safety syringes with safety syringes. Accordingly, there is a need to convert conventional non-safety syringes into safety syringes in a relatively inexpensive manner.